中文摘要：

为了确定施肥类型和施肥时间对中亚热带常绿阔叶林土壤有效氮和pH值的影响，通过在浙江天童木荷林（Schima superba）设置4种施肥处理（对照：不添加；氮添加：100 kg N·hm^-2·a^-1；磷添加：15 kg P·hm^-2·a^-1和氮磷添加100 kg N·hm^-2·a^-1＋15 kg P·hm^-2·a^-1），测定了氮磷添加后森林土壤有效氮和pH值的变化。结果表明：1）氮添加显著促进了土壤铵态氮和硝态氮含量的增加，增加幅度随着施氮时间的延长而增加；磷添加对土壤铵态氮含量无显著影响，但能显著降低土壤硝态氮含量；氮磷添加显著增加土壤硝态氮含量，随着施氮时间的延长，氮磷添加显著增加土壤铵态氮。2）随着施氮时间的延长，氮添加和氮磷添加均能显著降低土壤pH值；磷添加对土壤pH值无显著影响。3）相对硝态氮含量的增加而言，相同程度的土壤铵态氮含量的增加后土壤pH值降低的幅度更大。

英文摘要：

In order to understand the effects of N and P addition on soil available nitrogen and pH in a subtropical evergreen broadleaved forest dominated by Schima superba, we investigated contents of soil NH4^＋-N, NO3^--N and pH. Four N and P addition treatments were included as follows： CK （no addition of N and P）, N （50 kg N·hm^-2·a^-1）, P （15 kg P·hm^-2·a^-1） and NP （100 kg N·hm^-2·a^-1＋15 kg P·hm^-2·a^-1）. The results showed that： 1） The soil NH4^＋-N and NO3^--N concentrations were significantly increased after N addition, and the range of stimulation increased with prolonged nitrogen fertilization time. The soil NO3--N concentration was significantly decreased by P addition, and there was no significant impact on soil NH4＋-N concentration under P addition. NP addition significantly increased the soil NO3^--N concentration, and N addition alone had more obvious effects on the soil NO3^--N concentration than NP addition. The response of soil NH4^＋-N concentration to NP addition turned from insignificant to significant over time. 2） The soil pH decreased obviously with prolonged N addition and NP addition time, while remained stable under P addition. 3） Relative to the increase of nitrate nitrogen concentration, the same increase of soil ammonium nitrogen concentration resulted in a greater decline in pH value.